In recent years, the global warming problem has become noticeable; awareness about the environment on the part of nations, corporations and consumers has grown; and there has been an increasing trend to reduce the emission of global warming gas (CO2) that accompanies the consumption of energy. Therefore, renewable power sources, such as solar power generation (photovoltaic generation) and wind power generation (a wind farm), which do not generate global warming gas emissions, and which have limited adverse effects on the environment, and which generate power using natural energy, are attracting attention.
The amount of power generation in a renewable power source varies depending on the weather. Therefore a renewable power source is ordinarily operated by being linked to an electric power (distribution) system so that the quality of power supplied to a consumer is maintained. In that case, surplus power generated by the renewable power source and not consumed by the consumer is provided to the electric power system (reverse power flow) through a power line (transmission line). However, in a case where the consumer has such a contract with the electric power company that manages the electric power system such that there will not be any reverse power flow, the renewable power source is disconnected from the electric power system when surplus power is produced in the renewable power source. In some cases, a renewable power source is used with a storage battery to limit wasteful discarding of generated surplus electric power and to stabilize the amount of electric power supplied to a consumer. A consumer is a unit such as a house, a corporation, a building or a factory connected to an electric power system, which may also be an individual, a juridical person, a group, or the like who has a power-demand-supply contract with an consumption-supply contract with an electric power company. “Consumer” referred to in the following denotes both a unit such as the above-mentioned house, corporation, building or factory connected to an electric power system and an individual, a juridical person, a group, or the like who manages the house, corporation, building or factory, or denotes one from among the unit and the person or group managing the unit.
When supply of electric power from the electric power system to the consumer is stopped by an accident or the like (in a power outage), there is a need to stop the operation of the renewable power source operated by being linked to the electric power system or to disconnect the renewable power source from the electric power system in order to prevent the above-described reverse power flow. This is because if a reverse power flow from the renewable power source exists, voltage is generated in the power distribution line even during power outage to cause difficulty in ascertaining the cause of the occurrence of the power outage, and because the risk of an electric shock accident, a malfunction of electric facilities, or the like is increased due to access to the electric power system after recognition of the power outage.
On the other hand, it is desirable for the consumer to be able to use, just during the power outage, electric power generated by the renewable power source held by the consumer or electric power accumulated in a storage battery. Therefore a power conditioner that enables the renewable power source to be connected to the electric power system ordinarily has a function to disconnect the renewable power source from the electric power system (e.g., a circuit breaker). When the renewable power source is not connected to the electric power system, electric power can be supplied from an emergency receptacle provided on the power conditioner to a load by activating an autonomous operation function.
Patent Literatures 1 and 2, for example, describe configurations for supplying, during a power outage, electric power generated by a generator for private power generation or a gas cogeneration system to loads (electrical appliances) provided on the consumer side, each of which includes no renewable power source used in generation facilities.
Patent Literature 1 describes receiving online an expected restoration time from an electric power company in a power outage, and selecting loads (electrical appliances) to which electric power is to be supplied from a generator for private power generation according to whether the time taken to complete power restoration from the outage is short or long.
Patent Literature 2 describes accepting, upon the occurrence of a power outage, a predicted outage time period and predicted power demand fluctuation values with respect to loads, input by an operator, controlling the amount of power generation in a gas cogeneration system and the amount of electricity accumulated in a storage battery and the amount of discharge from the storage battery based on the predicted time and the predicted values, and selecting loads to which electric power is to be supplied.
As described above, when supply of electric power from the electric power system to the consumer is stopped (in a power outage), there is a need to stop operation of the renewable power source that is operated by being linked to the electric power system or to disconnect the renewable power source from the electric power system to prevent a reverse power flow.
Therefore, the power conditioner is ordinarily provided with a circuit breaker or the like for disconnecting the renewable power source from the electric power system when a power outage is detected. When the renewable power source is not connected to the electric power system, electric power can be supplied from the emergency receptacle to loads.
In ordinary cases, selection of the autonomous operation function is not automatically made when a power outage occurs, and there is a need for the consumer to activate the autonomous operation function. Also when the linking operation is performed by again linking the renewable power source to the electric power system at the time of power restoration from the outage, there is also a need for the consumer to stop the autonomous operation function and to link the renewable power source to the electric power system. Thus, there is a problem that the operation to change the operating mode of the renewable power source is burdensome.